CATV networks supply and distribute high frequency “downstream” signals from a main signal distribution facility, known as a “headend,” to premises (e.g., homes and offices) of subscribers of the CATV networks. The downstream signals can be provided to subscriber equipment, such as televisions, telephones, and computers. In addition, most CATV networks also receive “upstream” signals from subscriber equipment back to the headend of the CATV network. For example, a set top box can use an upstream signal to send information for selecting programs for viewing on a television. Also, upstream and downstream signals can be used by personal computers connected through the CATV infrastructure to the Internet. Further, voice over Internet protocol (VOIP) telephones can use upstream and downstream signals to communicate telephone conversations.
To permit simultaneous communication of upstream and downstream signals, and to permit interoperability of the subscriber equipment and the equipment associated with the CATV network infrastructure, the downstream and upstream signals are confined to two different frequency bands. For example, in CATV networks, the downstream frequency band can be within the range of about 54 to 1002 megahertz (MHz) and the upstream frequency band can be within the range of about 5 to 42 MHz.
Downstream signals can be delivered from the infrastructure of the CATV network to the subscriber premises via a network interface device (a.k.a., an entry device, an entry adapter, a terminal adapter, or a drop amplifier). A network interface device can be a multi-port device, in which an upstream entry port connects to a drop cable from the infrastructure of the CATV network, and one or more input/output ports (hereinafter “ports”) connect to subscriber equipment distributed around a premises of a subscriber.
The network interface device can include two paths: an active RF signal communication path (i.e., “active path”) and a passive RF signal communication path (i.e., passive path”). The active path can include active components (e.g., powered devices) that amplify and/or condition downstream signals received from the CATV infrastructure and conduct them to one or more ports of the CATV entry adapter. Subscriber equipment connected to these active ports benefits from this amplification of the CATV downstream signal. However, loss of power to the entry adapter prevents communication of active CATV signals by the active components. In comparison, the passive path lacks any active components. As such, subscriber equipment connected to these passive path can operate in the event of power loss. For example, the passive path may be used to provide a “lifeline telephone service” that remains operative when a subscriber premises losses power.